Valve rotating device

ABSTRACT

The invention relates to a valve rotator having an annular body in which are circumferentially provided several ball pockets having inclined ball races and in which a ball and a tangential spring are located in each case. In a rest position, the tangential springs press the balls at an upper point of the inclined ball races. An annular cover is also provided, which is rotatable and axially displaceable relative to the body. There is also an axial spring device between the body and the cover, the axial spring device pressing them apart axially in the rest position and if a valve spring tension is applied the body and the cover are pressed axially against one another and the balls roll along the ball races to a lower point. There is a clearly defined rotation between the body and the cover. A drastic reduction of wear is brought about in that the axial spring device is spaced from the balls and on one axial side of the axial spring device is provided a pivot bearing. The balls are in contact with the cover.

The invention relates to a valve rotator according to the preamble ofclaim 1.

In internal combustion engines, particularly large diesel engines, thevalve seat and valve stem are subject to strong wear. In order to bringabout a uniform thermal loading and abrasion, use is normally made of avalve rotator. Rotation additionally ensures the decarbonization of thevalve seat.

A valve rotator according to the preamble is known from U.S. Pat. No.2,624,323. In the latter case a disk spring is spaced from balls, whichproduce the rotary movement. In order to reduce the frictional forcesbetween the axial spring device and a cover, there is a three-pointsupport with inserted balls on one disk spring side.

In other conventional valve rotators, such as those of DE-AS 1 293 789,U.S. Pat. No. 2,827,886, DE-OS 27 57 455 or 30 04 320, the cover, whichis simultaneously the lower valve spring disk, is mounted in rotarymanner by means of a disk spring, which rests directly on the balls ofthe body. When the valve is closed the balls are held by the tangentialsprings at the upper point of the inclined ball race. If the valve isopened, the disk spring presses on the balls and the latter roll to thelowest point of the inclined ball race in the body. They rotate the diskspring and press together the tangential springs. The rotary movement ofthe disk spring is transferred via the cover, the valve spring, theupper spring disk and the shims to the valve. If the valve is closed,the disk spring is relieved. The balls are moved back into the startingposition again by the tangential springs without rolling.

Although this known valve rotator leads to a good rotation, its servicelife is limited, since the force introduction of the valve spring forcetakes place in the case of the known valve rotator via the disk springand the balls in the body. Thus, both on the balls and on the ball racesin the ball pockets considerable wear occurs and this is referred to aspitting. As a result of the function there is also a pronounceddeformation, bending and squeezing of the disk spring, particularly if aso-called overpressing occurs when the valve setting is not precise.

The object of the invention is to provide a valve rotator having asimple construction and a good rotation function, whilst at the sametime being subject to limited wear.

The invention achieves this object through a valve rotator having thefeatures of claim 1. Preferred further developments of the inventionappear in the dependent claims.

A fundamental idea of the invention is to separate from one another in alogical manner the rotation principle and the necessary forceintroduction and transfer principle. If the valve rotator is compressed,accompanied by the introduction of a valve spring force or tension, theaxial spring takes up the essential forces. As a result of the forcetransfer means constituted by the pivot bearing/axial springdevice/cover, the upper part of the valve rotator is frictionallyinterconnected under the valve spring tension. During a verticalmovement, reducing the spacing between the cover and the body, the outerface of the cover rotates the body via the antifriction or rollerbearing. This rotation takes place relative to the cover via frictionalengagement between the components cover—balls—body. In the case of aload removal these components are separated from one another,accompanied by an increase in the vertical spacing and as a result ofthe tension of the tangential springs the balls again assume theirstarting position. Thus, a further rotation of the body can be initiatedduring the next stroke. The antifriction bearing reduces friction andwear. Through the external arrangement of the balls, theircircumferential rolling forces as a result of the relatively largespacing from the rotation axis brings about a high torque, whichimproves rotation.

It is essential that the spring action and rotation of the rotator aredecoupled. As the axial spring device is arranged separately and inspaced manner with respect to the balls, the latter and the ball racesare scarcely axially loaded. In this way there is an extensiveelimination of pitting formation on the balls and in the ball pocketsand consequently wear on the valve rotator. The axial spring device isalso no longer exposed to bending, deformation and squeezing forces,which in the case of the known valve rotator occur on the known diskspring. The associated wear phenomena on the disk spring areconsequently largely avoided with the valve rotator according to theinvention. Compared with the known valve rotator, the valve rotatoraccording to the invention drastically improves the service life, whichconstitutes an enormous economic advantage, particularly with long-lifeinternal combustion engines. The antifriction bearing has as standardcomponents two bearing track rings between which the rolling elementsare located in a cage.

According to the invention the cover is mounted and guided about therotation axis relative to the body by the antifriction bearing. In thecase of an axial displacement of the cover relative to the body, therotary movement produced is exclusively radially guided by the needlebearing. There is no contact between the cover and the body. For saidradial guidance the axial needle bearing has conically positionedbearing track rings or lateral edge shoulders on the two bearing trackrings, between which are located the cylindrical, needle-like rollingelements with their cage.

Preferably, according to a further development of the invention, thereare three to six and preferably four ball pockets, which are uniformlydistributed along the circumference of the body. Compared withconventional valve rotators, according to the invention a much smallernumber of balls can be provided, because the individual balls arescarcely loaded or stressed. For a constant number of balls, roughlyeight to ten, the ball diameter can be roughly halved, so that it isbetween 3 and 10 mm. This considerably reduces costs during themanufacture of the body and the ball races therein.

Whereas in the case of the known valve rotator the inclination of theball races is relatively small, according to the invention it ispreferable for the inclination of the ball race of the ball pockets tobe uniform and namely between 6 and 15°. As a result of the limitedloading of the individual balls in the case of the valve rotatoraccording to the invention, the pre-requisite for a greater ball raceinclination is created, so that the rotary movement is improved.

According to a preferred embodiment of the invention, the axial springdevice comprises at least one disk spring, preferably a disk springunit. Disk springs represent a particularly cost-effective possibilityof pressing axially apart the cover and the body. When using a diskspring unit the desired axial forces can be inexpensively obtained withhigh precision.

The pivot bearing located on one axial side of the axial spring device,can be located either on the cover or on the body, the latter beingpreferred. The pivot bearing can be a simple slideway. However,according to the invention, it is preferable for the pivot bearing to bea needle bearing. In the case of this antifriction bearing variant, in asmall construction space there is a particularly low friction rotationbetween the disk spring supported frictionally on the body on the onehand and the cover on the other.

An overpressing of the valve rotator is inventively prevented in thatthe balls are completely received in the ball pocket on the lower pointof the ball race and that the body in this position engages against thecover. On reaching the maximum axial displacement path, the cover comesup against a block, so that the flux of force is directly passed by thecover into the body. An overstressing of the balls or the axial springdevice is consequently prevented, which also has a positive effect onthe service life of the valve rotator.

The body is firmly connected to the cylinder head, the cover serving asthe lower valve spring disk and is connected in non-rotary mannerthereto. However, it is also possible to have a reverse arrangement ofthe valve rotator according to the invention or a so-called upperarrangement in which the cover forms the upper valve spring disk.

The invention is described in greater detail hereinafter relative topreferred embodiments and the attached diagrammatic drawings, whereinshow:

FIG. 1 A diagrammatic cross-sectional view through a valve rotatoraccording to the invention.

FIG. 2 A diagrammatic plan view of the body of the valve rotator of FIG.1.

FIG. 3 A detail sectional representation of section A—A of FIG. 1 in therest position with the valve closed.

FIG. 4 A detail sectional view along section A—A of FIG. 1 on applying avalve spring tension with the valve open.

FIG. 5 A diagrammatic cross-sectional view of another embodiment of thevalve rotator according to the invention.

According to FIGS. 1 and 2 an inventive valve rotator 10 comprises anannular body 12, which has a central opening with a bevel seat 34 forreceiving a valve stem. In its radial ring region a needle bearing isprovided as the antifriction bearing 24. On a circumferential shoulderprojecting axially over the antifriction bearing 24 are uniformlycircumferentially distributed three ball pockets 14, in each of which isplaced a ball 16. A ball pocket base is constructed as an inclined ballrace 18 on which the ball 16 is held by a tangential spring 20 at anupper dead centre in a rest position.

On the antifriction bearing 24 is provided a single disk spring 32 as anaxial spring device 30. The axial spring device 30 is frictionallysupported on a disk-like cover 22, which rests on the balls 16. Theaxial position of the cover 22 relative to the body 12 is defined by acirclip 26, the cover 22 being rotatable relative to the body 12 and isalso axially displaceable to a certain extent towards the body 12. Onlyin said rest state is there a static friction between the cover 22 andthe body 12 via the circlip 26. During axial displacement andsimultaneous rotation, there is a guidance and consequently a clearlydefined position change, exclusively by means of the antifrictionbearing 24, which additionally prevents frictional wear.

The function of the valve rotator 10 is illustrated in FIGS. 3 and 4.For opening a not shown cylinder head valves a valve spring iscompressed and this exerts an axial force on the cover 22. The cover 22is displaced axially to the body 12 and, counter to the action of thetangential springs 20, the balls 16 are forced into the ball pockets 14.Whilst the balls 16 in a rest position have a clearly defined projectionor overhang with respect to the body 12, as can be gathered from FIG. 3,according to FIG. 4, when spring tension is applied, the ball 16 iscompletely pressed into the ball pocket 14. The ball 16 rolls on a ballrace 18 having an inclination between 6 and 15°, which leads to aclearly defined rotation of the cover 22 relative to the body 12.

With the valve rotator 10 according to the invention the cover 22 moveson block on the body 12, as can be gathered from FIG. 4, so that themaximum displacement path of the cover 22 is limited. A so-calledoverpressing and therefore damage to the balls 16 or ball races 18 isprevented.

Another preferred embodiment of a valve rotator 10′ according to theinvention can be gathered from FIG. 5. The essential components of thisembodiment correspond to the already described valve rotator 10, so thatthe correspondingly designated components will not be explained again.Unlike in the previously described embodiment, the axial spring device30′ is constituted by a disk spring unit comprising several disk springs32′ through which it is possible to set a clearly defined, high axialforce.

As a result of the valve rotator according to the invention with aseparate arrangement of the balls 16 and the axial spring device 30,compared with conventional rotators the balls 16 and ball races 18 aredrastically relieved, so that there is a large scale reduction ofundesirable deformation on said rotary components in the form ofpitting.

What is claimed is:
 1. Valve rotator comprising: an annular bodyprovided in a circumferential direction with plural ball pockets, eachball pocket including inclined ball races and each of which including aball and a tangential spring, the tangential spring in a rest positionholding the respective ball at an upper point of the respective inclinedball race; an annular cover rotatable about a rotation axis and axiallydisplaceable relative to the annular body; an axial spring devicepositioned between the annular body and the annular cover and configuredto press the annular body and the annular cover axially apart in therest position, and, if a valve spring tension is applied, the annularbody and annular cover are pressed axially against each other and theballs roll along the ball races to a lower point resulting in a definedrotation between the annular body and the annular cover, the balls beingin direct contact with the annular cover and spaced from the axialspring device radially to the rotation axis; and an antifriction bearingprovided between the axial spring device and the annular body or annularcover, the antifriction bearing supporting one axial side of the axialspring device, wherein, in a radial direction, the axial spring deviceis placed on an inside and the balls on an outside and are spaced fromone another.
 2. Valve rotator according to claim 1, wherein the annularcover is mounted to rotate about the rotation axis and guided relativeto the annular body by the antifriction bearing.
 3. Valve rotatoraccording to claim 1, wherein three to six ball pockets are provided andare uniformly distributed along the circumference of the annular body.4. Valve rotator according to claim 1, wherein four ball pockets areprovided and are uniformly distributed along the circumference of theannular body.
 5. Valve rotator according to claim 1, wherein theinclination of the ball race of the ball pockets is uniform and isbetween 6 and 15°.
 6. Valve rotator according to claim 1, wherein theaxial spring device comprises at least one disk spring.
 7. Valve rotatoraccording to claim 6, wherein the at least one disk spring includes adisk spring unit.
 8. Valve rotator according to claim 6, wherein theantifriction bearing includes a needle bearing.
 9. Valve rotatoraccording claim 1, wherein at the lower point of the ball race, theballs are completely received in the ball pocket and the annular body atthe lower point engages against the annular cover.